Hepatic Erythropoietin Gene Regulation by GATA-4
ABSTRACT Erythropoietin production switches from fetal liver to adult kidney during development. GATA transcription factors 2 and 3
could be involved in modulating this switch, because they were shown to negatively regulate erythropoietin gene transcription
through a promoter proximal GATA site. Herein, we analyzed the role of several GATA factors in the regulation of the erythropoietin
gene in human liver and in hepatoma cells. Although GATA-3 expression in hepatocytes increases during human development, erythropoietin
mRNA accumulation is unaltered in mutant mice lacking GATA-3. We found that GATA-2, -3, -4, and -6 are all expressed in human
hepatocytes and that GATA-4 exhibits the most prominent Epo promoter binding activity in vitro and in vivo. Inhibition of GATA-4 expression by RNA interference leads to a dramatic reduction in Epo gene transcription in Hep3B cells.
Moreover, GATA-4 expression is high and limited to hepatocytes in the fetal liver, whereas GATA-4 expression in the adult
liver is low and restricted to epithelial cells surrounding the biliary ducts. Thus, GATA-4 is critical for transcription
of the Epo gene in hepatocytes and may contribute to the switch in the site of Epo gene expression from the fetal liver to
the adult kidney.
- SourceAvailable from: Edward T Bagu
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- "Incidentally, GATA-4 was shown to be absent in hepatocytes that were isolated from normal mice and humans during the postnatal period (Dame et al. 2004, Divine et al. 2004). The absence of GATA-4 in hepatocytes during the postnatal period was also cited as the reason for the switch in the expression of the EPO gene from fetal hepatocytes to the adult kidney in mice and humans (Dame et al. 2004). The changes in concentrations of the proinflammatory cytokines (IL6) in the body during the postnatal period may therefore affect levels of either GATA-6 or FOG protein (1 and 2) in hepatocytes and the nature of the response being dependent on the type and strength of the input signal: the increase in GATA-6 with or without a decrease in FOG upregulating the transcription of HAMP; while the increase in concentration of FOG proteins with or without a decrease in GATA-6 concentrations downregulating the transcription of HAMP. "
ABSTRACT: Hepcidin is an antimicrobial peptide hormone involved in the metabolism of iron, encoded for by the HAMP gene mainly in hepatocytes. It's expressed at lower levels in other cells such as the macrophages. The mechanisms that determine tissue-specific expression of hepcidin remain unclear. GATA- and its co-factor Friend of GATA (FOG) modulate the tissue-specific transcription of other genes involved in the metabolism of iron. GATA proteins are group of evolutionary conserved transcriptional regulators that bind to the consensus motif -WGATAR- in the promoter. We characterized a 1.3 kb fragment of the 5'-flanking sequence of the HAMP gene in Huh7 cells, which express HAMP. Transfection of 5'-deletions of the HAMP promoter in Huh7 cells revealed two regions, -932/-878 and -155/-96, that when deleted decreased promoter activity. Using site-directed mutations in the HAMP promoter region -155/-96 we identified two subregions, -138/-125 and -103/-98, which when mutated suppressed promoter activity by 70 and 90% respectively. Site -103/-98 with a sequence -TTATCT- to which endogenous GATA proteins 4 and 6 bind and transactivate HAMP is a GATA-regulatory element (RE). Mutation of the GATA-RE abrogated binding of GATA proteins 4 and 6 to the promoter and blunted the GATA transactivation of HAMP. FOG proteins 1 and 2 suppressed the endogenous and exogenous GATA activation of the HAMP promoter. We concluded that the GATA-RE, -TTATCT- in the HAMP promoter region -103/-98 is crucial for the GATA-4 and GATA-6 driven transcription of hepcidin in Huh7 cells and that FOG proteins moderate the transcription by suppressing the GATA transactivation of HAMP.Journal of Molecular Endocrinology 12/2011; 47(3):299-313. DOI:10.1530/JME-11-0060 · 3.62 Impact Factor
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- "In addition to the heart and gonads, GATA-4 has been detected in a limited number of other tissues. These include liver, pancreas, stomach and intestine (Gao et al., 1998; Dame et al., 2004; Ketola et al., 2004). Given this wide distribution and suggested roles for GATA-4 in several regulative pathways, impaired GATA-4 function can cause variable, unrelated conditions. "
ABSTRACT: Of the six GATA transcription factors, GATA-4 and GATA-6 are expressed in the mouse and human adrenal with distinct developmental profiles. GATA-4 is confined to the fetal cortex, i.e. to the less differentiated proliferating cells, while GATA-6 is expressed both in the fetal and adult adrenal. In vitro, GATA-4 regulates inhibin-alpha and steroidogenic factor-1 implicated in normal adrenal function. GATA-6 probably has roles in the development and differentiation of adrenocortical cells, and in the regulation of steroidogenesis. GATA-4 expression is dramatically upregulated and GATA-6 downregulated in gonadotropin dependent mouse adrenocortical tumors. This is accompanied by the appearance of luteinizing hormone receptor (LHR). In vitro, GATA-4 transactivates LHR promoter, and gonadotropins upregulate GATA-4 levels. Human adrenal tumors occasionally express GATA-4, whereas GATA-6 levels are usually lower than normal.Molecular and Cellular Endocrinology 03/2007; 265-266:17-22. DOI:10.1016/j.mce.2006.12.033 · 4.24 Impact Factor
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- "Although both murine and human claudin-2 promoters contain a putative GATA interacting site (Sakaguchi et al., 2002), the relation between GATA binding protein (GATA) members and claudin-2 regulated expression remains unexplored. Members of this transcription factor family are expressed in the intestine as well as in various other tissues where they play critical roles in regulating tissue specific gene expression (van Wering et al., 2002; Dame et al., 2003; Eisbacher et al., 2003; Jimenez et al., 2003). GATA-4 has been shown to interact functionally with CDX2 and HNF-1a to modulate several intestine specific genes (Boudreau et al., 2002b) and could be involved in claudin-2 regulation. "
ABSTRACT: Claudins, and particularly claudin-2, are important regulatory components of tight junction permeability. A better understanding of the involvement of claudin-2 in intestinal barrier functions requires the characterization of its distribution and regulation in the intestine. Interestingly, the claudin-2 gene promoter harbors a number of similarities to that of sucrase-isomaltase, a marker of enterocyte differentiation. We thus investigated the expression of claudin-2 in relation to the transcription factors CDX2, HNF-1alpha, and GATA-4 in the human intestine. The characterization of claudin-2 and the expression of the above transcription factors were performed by immunofluorescence, Western blot, and RT-PCR in the developing human intestinal epithelium. The functional role of CDX2, HNF-1alpha, and GATA-4 on claudin-2 regulation was also examined by ectopic expression studies in intestinal cell models. Claudin-2 was detected in both crypt and villus cells of the small intestine but restricted to undifferentiated crypt cells in the colon. CDX2 and HNF-1alpha were expressed along the entire intestine whereas GATA-4 was undetectable in the colon. Accordingly, in the colonic Caco-2 cell model, claudin-2 was found to be present only in undifferentiated cells. Like in the colonic epithelium, GATA-4 was found to be also lacking in Caco-2 cells while CDX2 and HNF-1alpha were present at significant levels. Cotransfection experiments showed that the claudin-2 promoter was activated by CDX2, HNF-1alpha, and GATA-4 in a cooperative manner. Furthermore, forced GATA-4 expression in Caco-2 cells enhances maintenance of claudin-2 expression during differentiation. These observations suggest that optimal claudin-2 expression in the gut relies on the presence of GATA-4, suggesting a role for this factor in intestinal regionalization.Journal of Cellular Physiology 04/2005; 203(1):15-26. DOI:10.1002/jcp.20189 · 3.87 Impact Factor